塔里木盆地古城东工区三维地震成像技术及应用

3D Seismic Imaging Technology and Its Application in GCD Work Area of Tarim Basin

塔里木盆地古城东工区被沙漠覆盖,受松散的厚沙丘结构影响,采集的地震资料叠加了较强能量的沙丘鸣震噪声,导致奥陶系海相礁滩体储集层不能准确成像。针对传统成像方法存在的分辨率低、成像不聚焦等问题,在保真地震资料处理基础上,利用“三步法”沙丘鸣震噪声衰减技术对其进行大幅衰减。采用三维频率空间域叠前随机噪声压制技术提高叠前预处理道集的信噪比,并充分利用垂直地震剖面速度、测井信息、解释层位等资料,开展多信息约束网格层析建模和各向异性逆时偏移。结果表明:沙丘鸣震噪声得到衰减,叠前地震资料信噪比较传统去线性噪声方法明显提高;叠前道集中残余的地震随机噪声得到有效压制,处理后道集的速度谱能量更聚焦,有利于速度模型的精准建立;在高密度地震成像道集基础上,进行反演网格由粗到细逐级细化的深度域模型反演,构建的速度模型能够精细刻画奥陶系海相礁滩体储集层;采用各向异性逆时偏移方法实现了奥陶系海相礁滩体储集层复杂波场的准确归位,提高其分辨率和聚焦度。研究成果支撑了古城东工区G1井侧钻轨迹的优化设计,并得到了实钻验证,可为塔里木盆地沙漠区域同类地震资料的高精度成像处理提供技术支撑。

The GCD work area of the Tarim basin is covered by desert,where the acquired seismic data are superimposed with high-energy sand dune resonance noise due to the loose and thick dune structures,hampering the accurate imaging of the Ordovician marine reef-beach reservoir.Conventional imaging methods are disadvantageous due to low resolution,defocusing and other defects.On the basis of fidelitybased seismic processing,a three-step method for substantial attenuation of the sand dune resonance noise was incorporated.The 3D frequency space domain pre-stack random noise suppression technology was adopted to enhance the signal-to-noise ratio(SNR)of pre-stack preprocessing gathers.Furthermore,vertical seismic profile velocity,logging data,and interpreted horizons were combined to enable a multiinformation-constrained grid tomography modeling and anisotropic reverse time migration.The results show that the sand dune resonance noise is effectively attenuated,and the SNR of pre-stack seismic data is significantly improved as compared to conventional denoising methods.The residual random seismic noise in pre-stack gathers is effectively suppressed,and the post-processing energy in velocity spectra of the gathers is more focused,facilitating precise velocity model establishment.Based on the high-density seismic imaging gathers,depth-domain model inversion where the inversion grid is gradually refined from coarse to fine was performed,and the established velocity model can accurately characterize the Ordovician marine reef-beach reservoirs.Anisotropic reverse time migration accurately relocated the complex wavefields of the Ordovician marine reef-beach reservoirs,enhancing resolution and focusing.The research results provide a support for optimizing the design of the sidetracking trajectory for Well G1 in the GCD work area,which was validated by actual drilling results.These techniques can provide a robust technical support for high-precision imaging and processing of seismic data in desert areas of the Tarim basin.